1. Field of the Invention
This invention relates to a tape cassette, in particular a video tape cassette, of the kind having a housing, at least one tape reel, a front wall and a pressure spring which exerts a spring force on said at least one tape reel in the direction of a defined operating position, the housing comprising at least two housing parts which are connected to one another by connecting means. The invention also relates to a pressure spring for such a tape cassette.
2. Description of Related Art
In all commercially available video cassettes of the VHS and Beta video systems, as well as in the comparatively new 8 mm video cassette, coplanar reels are pressed toward the lower half of the housing by curved springs which are fastened inside the upper half of the housing and have been punched out of spring sheet material. Hence, when such a cassette is placed in the appropriate playback apparatus, the reels lie evenly on the hub holders of the apparatus and run smoothly when the tape is played back. All such reel pressure springs have the same function, but their sizes and their spring powers may differ in different cassettes depending on the cassette size, the reel size and the reel spacing.
Each pressure spring is usually manufactured by punching it out of spring steel strip in an advantageous manner to save material and in a rapid punching sequence.
German Utility Model No. 8,418,178 describes a pressure spring for, for example, VHS cassettes, which can be suspended from a window of the cassette housing by means of an integral hook, the pressure spring being attached in such a manner that it cannot be lost, e.g. during manufacture. The disadvantage with this known pressure spring is that the cassette window is inevitably partially obscured. German Laid-Open Patent Application DOS No. 3,329,890 discloses a plate spring for a video cassette which is not welded to the upper housing part but which is held in position by means of a cylindrical pin which is located on the lower cassette part and which projects into a locating hole in the upper housing part when the cassette is closed. However, before the cassette is assembled and when the housing is open, the spring lies loosely in the upper housing part and can slip or fall out, inevitably resulting in problems during manufacture or operation. Other disadvantages of this known pressure spring are that the dimensions of the housing parts have to be matched very precisely with one another, which presents problems and is expensive where large numbers are involved, and that the sprng pushes the housing parts apart as a result of its spring action, so that the cassette may open up after a certain time due to the plastic yielding.